There's a clear contradiction in the statements.
As per UCI, "The UCI regrets that certain teams have objected to the test by not nominating a rider to carry the tracking device".
As per the teams, "We made clear that ... The UCI or its partner was free to select a rider and install the device at their own liability".
So, sounds as if the teams wanted to shift the responsibility for selecting the test rider to UCI, while UCI insisted on the teams to do so. I am quite sure both parties had some background motives. But still surprised that UCI proceeded with the dsq - how can they justify it to the organizer? The race lost the best third of its competitors just like that..
It makes sense that the teams select the rider or otherwise you may have a dispute if the UCI selects the rider. Even though they ended with a dispute.